Electron tube



Dec. 25, 1945. w, w, EI ETAL 2,391,690

ELECTRON TUBE Original Filed March 21, 1944 3 Sheets-Sheet l INVENTORS Wf/l/am W. E H'e/ By dack AMECu/l 9h 7 ATTORNEY DCQ. 25, 1945. w w rr ETAL 2,391,690

ELECTRON TUBE Original Filed March 21, 1944 3 Sheets-Sheet 2 INVENTORS William W. Ei'f'el duck .MECU/kfgh BY g ATTORNEY ea. 25, 1945. w, w ElTEL ET AL 2,391,690

ELECTRON TUBE Original Filed March 21, 1944 5 Sheets-Sheet 3 INVENTORS Wi/l/am 14/. E/fe/ BY Jack A. M? Cu/muy/i ATTO/QNEY Patented Deal 25, 1945 'ELECTRON runn- William w. mm, Woodslde, and Jack A. McCullough, Mlllbrae, Calif., assignors to Eitel- McCullough, Inc., San Bruno, Calii., a corporation of California Original application March 21, 1944, Serial No.

527,474. Divided and this 1945, Serial No. 607,480

9 Claims. (Cl. 250-275) This is a division of our copending application Serial No. 527,474.

Our invention relates to multi-grid tubes and more particularly to tetrodes.

It is among the objects of our invention to provide a multi-grid tube structure which facilitates assembly and insures accurate spacing and alignment between the electrodes.

Another object is to provide animproved arrangement of and mounting for the electrodes.

A further object is to provide impro ements in the grid structures.

The invention possesses other objects and features of advantage, some of which, with the fore-. going, will be set forth in the following description of our invention. It is. to be understood that we do not limit ourselves to this disclosure of species of our invention as we may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawings:

Figure'l is a perspective view of a tube embodying the improvements of our invention; and

, Figure 2 is a vertical sectional view of the same.

Figure 3 is a horizontal sectional view, taken in a plane indicated by line 3-3 of Figure 2, with the shield omitted; and

Figure 4 is an enlarged detail sectional view showing the cathode and grids, taken in a plane indicated by line 4--.l of Figure 2.

In terms of broad inclusion, our tube com prises a sectional envelope, a tubular anode in the envelope, a seal joining the envelope sections in a plane transverse to the axis of the anode, conductor means connected to the anode and. supported by a section of the envelope lying at one side of the sealing plane, a cathode and pair of grids extending within the anode, and conductor means connected to the cathode and grids and supported by a section of the envelope lying on the opposite side of the sealing plane. The two grids, functioning as control and screen grids, are interposed between the cathode and plate with the elements of one grid radially aligned with those of the other grid. The electrical characteristics of our multi-grid tube are further improved by incorporating electrodes having special properties regarding electron emission.

In greater detail, and referring to the drawings, our tube comprises a vitreous envelope of glass or the like having an upper section 2 and a lower section 3 fused together along a seal 4 in a plane transverse to the longitudinal axis of the envelope. Prior to sealing together, the enapplication July 27,

velope sections are cup-shaped, each having an open end for convenience in assembling the internal parts. Exhaust tubulation 6 is preferably arranged at the center of the lower section.

The multi-grid tube illustrated is -a tetrode having four electrodes including an anode 1, screen grid 8, control grid 9 and cathode ll. These electrodes are concentric about an axis lying normal to the plane of seal 4. Anode I is tubular in form, preferably cylindrical, with heat radiating fins 12. It is open at the bottom and preferably closed at the top by a cap l3 welded to the rim. This cap protects the upper end of the envelope against bombardment and also functions as part of the mounting for the anode.

Anode l is mounted on a lead-in conductor or lead l4 sealed to and supported by upper envelope section 2 at seal I6. This lead projects into the envelope along the axis of the electrodes, terminating short of cap l3. A conical bracket 11 completes the support and has its diverging end welded to cap l3 and its converging end welded to lead I4. Y

The remaining electrodes are all supported by lower envelope section 3. As shown in Figures 2 and 3, cathode leads [8, screen grid leads I9 and control grid lead 2! are vertically disposed in a circle projecting into the lower end of the envelope through seals 22. Leads 19 are spaced on opposite sides of center and control grid lead turned legs welded to the ends of cathode leads I8.

Control grid 9 is preferably of cage-type construction comprising longitudinal or vertical wire bars 24 held by a helical wire winding 26, which grid elements terminate in' a base ring 21. This inner grid projects into the anode along the cathode and is supported by a strap 28 welded to base ring 21 and to an angle bracket 29 which in turn is welded to lead 2 I Screen grid 8 is also of cage-type construction comprising longitudinal bars 3| held'by a helical winding 32, which grid elements terminate in a base ring 33. Mounting for this outer grid is provided by a metallic shield member 34 secured to leads l9 by bracket pieces 36 and having a central aperture 31 registering with grid ring 33. A collar 38 welded to the shield and to' ring 33 connects these parts.

Shield 34 extends transversely of the electrodes and is substantially coextensive with the cross-'- sectional area oi the envelope. It is preferably shaped like an inverted pan with a peripheral flange is spaced close to the inner surface of the envelope. By this arrangement the conductors in the lower part of the tube are eilectively shielded from the anode.

The base for the tube comprises a metallic ring 4| secured to the envelope by cement 42 and carrying an insulating disk 43 from which prongs 44 project. These depending prongs are coaxially aligned with the leads and are hollow to receive lead extension sleeves 40 which are soldered to the prong tips at 41. This basing provides a compact arrangement with short direct connections from the prongs to the leads enteringthe envelope.

Another feature is that external ring .00- acts with internal shield 34 to form a metallic housing structure which confines and completely shields the lower region'oi the envelope. The

inverted cup-shaped structure is clearly shown in Figures 1 and 2. wherein internal part 34 forms the top and external part 4! forms the side wall of the cup. This metallic structure houses the cathode and grid conductors, isolating them from the plate.

Another feature of our improved tube is that the elements of the grids are radially aligned. As shown in Figures 2 and 4, longitudinal bars 24 and SI of the control and screen grids are aligned one behind the other, along radii extending from the axis oi the electrodes. Likewise, helical windings 32 and 28 are radially aligned so that, looking from the cathode, convoiutions on the screen grid lie behind those on the control grid. The screen grid is thus shielded from the electron stream by the control grid, which shading of the screen materially improves the tube characteristics. We have compared tubes identical in all respects except that the grid elements in one tube were aligned while the grid elements in the other tube were misaligned. In the tube having aligned grid elements the screen grid draws materially less current than in a tube having misaligned grid elements.

The screen grid may be coated to provide a suitable surfacing composition indicated at ii, the nature of which forms no part of the instant invention.

We claim:

1. An electron tube comprising an envelope, a tubular anode in the envelope, a cathode extending into the anode, a grid assembly consisting of an inner grid and outer grid interposed between the cathode and anode, an anode lead projecting into the upper' portion of the envelope, means supporting the anode on said lead, cathode and rid leads projecting into the lower portion 01 the envelope, means supporting the cathode on the cathode leads, means supporting the inner grid on a grid lead, and a shield carrying the outer grid and supported on the envelope.

2. An electron tube comprising an envelope, a tubula anode disposed about a vertical axis in the envelope, 9. vertical anode lead projecting into the upper portion of the envelope, means supporting the anode on said lead, a cathode extending into the anode, a grid assembly consisting of an inner grid and outer grid interposed between the cathode and anode, vertical cathode and grid leads projecting into the lower portion of the envelope, means supporting thecathode on the cathode leads, means supporting the inner a grid lead, and a shield carrying the outer grid and supported on the envelope.

3. An electron tube comprising an envelope, a tubular anode in .the envelope. a cathode and control grid and screen grid extending into the anode, each of said grids having an upper free end and a lower terminal end, an anode lead projecting into the upper portion 01' the envelope,

means supporting the anode on said lead, cathode and grid leads projecting into the lower portion or the envelope, means supporting the cathode on the cathode leads, means supporting the control grid on one of the grid leads, and a shield carrying the screen grid and supported on the envelope.

4. An electron tube comprising an envelope, a transverseshicld in the envelope having an aperture therein, a tubular anode in the envelope above the shield, conductor means for the anode projecting into the envelope above the shield, a screen grid having a lower end registering with the shield aperture and extending upwardly within the anode, a cathode and control grid ex,- tending upwardly within said screen grid, and conductor means for the cathode and control grid projecting into the envelope below said shield, said last mentioned conductor means including a cathode supporting member extending through said shield aperture.

a0 5. An electron tube comprising an envelope, a

transverse shield in the envelope having an aperture therein, a tubular anode in the envelope above the shield. conductor means for the anode projecting into the envelope above the shield, a

as screen grid having a lower end registering with the shield aperture and extending upwardly within the anode, a cathode and control grid extending upwardly within said screen grid, cond-uctor means for the cathode and control grid projecting into the envelope below said shield,

and a base including a metallic ring encircling the lower portions 01' the envelope with its upper edge lying adjacent the periphery of said shield.

6. An electron tube comprising an envelope, a transverse shield in the envelope having an aperture therein, a tubular anode in the envelope above the shield, conductor means for the anode projecting into the envelope above the shield, a screen grid having a lower end registering with the shield aperture and extending upwardly within the anode, a cathode and control grid extending upwardly within said screen grid, conductor means for the cathode and control grid projecting into the envelope below said shield, and a base including a metallic ring encircling the lower portions of the envelope, said shield being substantially coextensive with the cross-sectional area of the envelope and having a peripheral edge lying close to said ring.

7. A tetrode comprising an envelope, a transverse shield in the envelope having an aperture therein, a tubular anode in the envelope above the shield, conductor means for the anode projecting into the envelope above the shield, a grid assembly consisting of an inner control grid and an outer screen grid extending upwardly within the anode, each 01 said grids having an upper free end and a lower terminal end, the lower end or the screen grid being connected to the shield in registration with said aperture, a cathode extending upwardly within .the' screen grid, and conductor means tor the cathode and control grid projecting into the envelope below the shield.

8. A tetrode comprising an envelope, a transverse shield in the envelope having an aperture therein, a tubular anode in the envelope above the shield, conductor means for the anode projecting into the envelope above the shield, a grid assembly consisting of an inner control grid and an outer screen grid extending upwardly within the anode, each of said grids having an upper 'free end and a lower terminal end, the lower end of the screen grid connected to the shield in registration with said aperture, a cathode extending upwardly within the screen grid, and conductor means for the cathode and control grid projecting into the envelope below the shield, each grid having longitudinal bars, the longitudinal bars of one grid being arranged in radial alignment with the longitudinal bars of the other grid.

9. A tetrode comprising an envelope, a transverse shield in the envelope having an aperture therein, a tubular anode in the envelope above the shield, conductor means for the anode projecting into the envelope-above the shield, a grid assembly consisting of an inner control grid and an outer screen grid extending upwardly within the anode, each of said grids having an upper free end and a lower terminal end, the lower end of the screen grid being connected to the shield in registration with said aperture, 9. cathode extending upwardly within the screen grid, and conductor means for the cathode and control grid projecting into th envelope below the shield, said envelope including upper and lower sections sealed together in a plane transverse tow the axis of the envelope.

- WILLIAM W. EITEL.

JACK A. McCULLOUGH. 

